SymbolSymbol NameMeaning / definitionExample
angleformed by two rays∠ABC = 30°
measured angle ABC = 30°
spherical angle AOB = 30°
right angle= 90°α = 90°
°degree1 turn = 360°α = 60°
degdegree1 turn = 360degα = 60deg
primearcminute, 1° = 60′α = 60°59′
double primearcsecond, 1′ = 60″α = 60°59′59″
lineinfinite line 
ABline segmentline from point A to point B 
rayline that start from point A 
arcarc from point A to point B = 60°
perpendicularperpendicular lines (90° angle)AC ⊥ BC
| |parallelparallel linesAB | | CD
congruent toequivalence of geometric shapes and size∆ABC≅ ∆XYZ
~similaritysame shapes, not same size∆ABC~ ∆XYZ
Δtriangletriangle shapeΔABC≅ ΔBCD
|xy|distancedistance between points x and yxy | = 5
πpi constantπ = 3.141592654…

is the ratio between the circumference and diameter of a circle

c = π·d = 2·π·r
radradiansradians angle unit360° = 2π rad
cradiansradians angle unit360° = 2π c
gradgradians / gonsgrads angle unit360° = 400 grad
ggradians / gonsgrads angle unit360° = 400 g